[v7.0/forgejo] chore(release): next-digest moved to invisible.forgejo.org (#7724)

**Backport:** https://codeberg.org/forgejo/forgejo/pulls/7720

In order to improve the security of the Forgejo infrastructure the next-digest repository was moved to a private instance.

## Testing

- After the merge, trigger a mirror to build a new v12.0-test release
- Verify in experimental that the workflows works as expected
- Verify v12.next.forgejo.org is upgraded with the latest commit
- Once the test completes
    - Tag for backport to v11 & v7
    - Manual backport to v7 because it conflicts

Co-authored-by: Earl Warren <contact@earl-warren.org>
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/7724
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Co-authored-by: forgejo-backport-action <forgejo-backport-action@noreply.codeberg.org>
Co-committed-by: forgejo-backport-action <forgejo-backport-action@noreply.codeberg.org>

.forgejo/workflows/publish-release.yml

@@ -2,6 +2,8 @@
 #
 # See also https://forgejo.org/docs/next/developer/RELEASE/#release-process
 #
+# TOKEN_NEXT_DIGEST is a token with write repository access to https://invisible.forgejo.org/infrastructure/next-digest issued by https://invisible.forgejo.org/forgejo-next-digest
+#
 # https://codeberg.org/forgejo-experimental/forgejo
 #
 #  Copies a release from codeberg.org/forgejo-integration to codeberg.org/forgejo-experimental
@@ -14,7 +16,7 @@
 #  vars.DOER: forgejo-experimental-ci
 #  secrets.TOKEN: <generated from codeberg.org/forgejo-experimental-ci>
 #
-# http://private.forgejo.org/forgejo/forgejo
+# http://invisible.forgejo.org/forgejo/forgejo
 #
 #  Copies & sign a release from codeberg.org/forgejo-integration to codeberg.org/forgejo
 #
@@ -80,6 +82,6 @@ jobs:
       - name: upgrade v*.next.forgejo.org
         uses: https://code.forgejo.org/infrastructure/next-digest@v1.1.0
         with:
-          url: https://placeholder:${{ secrets.TOKEN_NEXT_DIGEST }}@code.forgejo.org/infrastructure/next-digest
+          url: https://placeholder:${{ secrets.TOKEN_NEXT_DIGEST }}@invisible.forgejo.org/infrastructure/next-digest
           ref_name: '${{ github.ref_name }}'
           image: 'codeberg.org/forgejo-experimental/forgejo'